Method and apparatus for assigning data to split bearers in dual connectivity

ABSTRACT

A method and an apparatus for adjusting an amount of data to be assigned to a secondary base station in dual connectivity are provided. The method includes receiving, via an X2 interface between the first base station and a second base station from the second based station, first information on a buffer for an evolved universal terrestrial radio access network (E-UTRAN) radio access bearer (E-RAB), second information on a buffer for a terminal which is associated with the first base station and the second base station, and third information on packets lost in X2 transmission between the first base station and the second base station, and adjusting an amount of data to be assigned to the second base station based on the first information, the second information and the third information.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 14/747,409, filed on Jun. 23, 2015, which claims the benefit under35 U.S.C. § 119(a) of a Chinese patent application filed on Jun. 23,2014 in the State Intellectual Property Office and assigned Serialnumber 201410283197.4, and of a Chinese patent application filed on Sep.25, 2014 in the State Intellectual Property Office and assigned Serialnumber 201410497636.1, the entire disclosure of each of which is herebyincorporated by reference.

TECHNICAL FIELD

The present disclosure relates to wireless communications. Moreparticularly, the present disclosure relates to a method and anapparatus for assigning data to split bearers in dual connectivity.

BACKGROUND

Modern mobile communications are tending to provide high speedtransmission of multimedia services for users.

FIG. 1 is a schematic diagram illustrating a structure of a systemarchitecture evolution (SAE) system according to the related art.

Referring to FIG. 1, in the system, a user equipment (UE) 101 is aterminal device which receives data. An evolved universal terrestrialradio access network (E-UTRAN) 102 is a wireless access network whichincludes evolved Node Bs (eNBs)/NBs which provide UEs with interfacesfor accessing the wireless network. A mobility management entity (MME)103 manages mobility context, session context and security informationof UEs. A service gateway (SGW) 104 provides user plane functions. TheMME 103 and SGW 104 may reside in the same physical entity. A packetdata network (PDN) gateway (PGW) 105 implements functions includingaccounting, lawful interception and so on, and may reside in the samephysical entity with SGW 104. A policy and charging rule functions(PCRF) 106 provides quality of service (QoS) policies and chargingrules. A serving general packet radio service (GPRS) support node (SGSN)108 is a network node device providing routing for data transmission inthe universal mobile telecommunications system (UMTS). A home subscriberserver (HSS) 109 is a home sub system of the UE, and maintains userinformation including a current location of the UE, the address of theserving node, user security information, packet data context of the UE,and so on.

In long term evolution (LTE) systems of the related art, each cellsupports a maximum bandwidth of 20 MHz. LTE-advanced systems adoptcarrier convergence to increase peak data rate of UEs. With the carrierconvergence technique, a UE may at the same time communicate withmultiple cells that are working at different carrier frequencies underthe control of one eNB, which provides a maximum transmission bandwidthof 100 MHz, therefore uplink/downlink peak data rate can be increased byseveral times.

In order to increase the transmission bandwidth, multiple cells mayprovide service for the same UE. The multiple cells may from the sameeNB or from different eNBs. The technique is referred to as carrieraggregation, or dual connectivity.

FIG. 2 is a schematic diagram illustrating a cross-eNB carrierconvergence mechanism according to the related art.

Referring to FIG. 2, for a UE working under carrier aggregation,aggregated cells includes a primary cell (PCell) and at least onesecondary cell (SCell). There is only one PCell, and the PCell is alwaysactivated. The PCell can only be changed through a handover process, andNAS information is only transmitted and received by the UE through thePCell. Physical uplink control channel (PUCCH) can only be transmittedby the PCell. The PCell and the SCell may from different eNBs. The eNBto which the PCell belongs is referred to as a master eNB (MeNB), andthe eNB to which the SCell belongs is referred to as a Secondary eNB(SeNB). The MeNB and the SeNB are connected with each other through anX2 interface.

The dual connectivity mechanism provides two manners of establishingbearers. One manner is referred to as split bearer, i.e., a data bearerfrom the core network to an MeNB is split into two radio bearers whichare respectively established on the MeNB and an SeNB. The MeNB performsdata splitting, and transmits data packets assigned to the SeNB via theX2 interface to the SeNB. The UE receives downlink data simultaneouslyfrom the radio bearers on the MeNB and the SeNB. Regarding downlinkdata, when an MeNB receives data from the core network, the MeNBperforms data encryption, and splits the data packets of packet dataconvergence protocol (PDCP) so that one part of the data packets aretransmitted to the UE via the radio bearer on the MeNB while the otherpart of the data packets are transmitted to the UE via the radio beareron the SeNB. The MeNB decides the amount of data packets transmittedrespectively by the MeNB and the SeNB, i.e., deciding data packets thatare to be transmitted by the MeNB and data packets that are to betransmitted by the SeNB. A properly decided proportion can effectivelyincrease data throughput of the UE. An improper proportion may causedelay in sequencing received data, which reduces data throughput.Therefore, the SeNB is required to report information to the MeNB forthe MeNB to decide a proper data split ratio, i.e., deciding the amountof data packets to be transmitted via the SeNB. The information mayinclude the quality of the radio channel between the SeNB and the UE,information about the capacity of available buffer in the SeNB, and thelike.

Currently, there is no specification as to whether the capacity of databuffer refers to the capacity allocated for a UE or for a bearer. Bufferof different eNBs may be implemented differently. Some manufacturersproduce eNBs that allocate buffer according to UEs, while othermanufacturers produce eNBs that allocate buffer according to bearers.Therefore, there is no mechanism that can accommodate the differences ofeNBs and provide a flexible manner for reporting the information. Thepresent disclosure provide a method which can better adapt to differentimplementation manners of eNBs produced by different device providers,effectively use data bearer bandwidth, and reduce data transmissiondelay.

Therefore, a need exists for a method and an apparatus for assigningdata to split bearers in dual connectivity which can better adapt todifferent implementation manners of eNBs, effectively use data bearerbandwidth, and reduce data transmission delay.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and an apparatus for assigning data tosplit bearers in dual connectivity which can better adapt to differentimplementation manners of eNBs, effectively use data bearer bandwidth,and reduce data transmission delay.

In accordance with an aspect of the present disclosure, a method ofassigning data to split bearers in dual connectivity is provided. Themethod includes receiving, by a master evolved Node B (MeNB) of a userequipment (UE) via an X2 interface between the MeNB and a secondary eNB(SeNB), information of available buffer decided by the SeNB, decidingthe available buffer is available buffer for the UE or available bufferfor an enhanced radio access bearer (E-RAB) on the SeNB according to anindicator in the information of the available buffer or according to abearer that transported the information of the available buffer, andadjusting, by the MeNB, the amount of data assigned to the SeNBaccording to the received information of the available buffer.

In accordance with another aspect of the present disclosure, a method ofan MeNB receiving information of an available buffer is provided. Themethod includes receiving, by the MeNB via a user data bearer on the X2interface, the information of the available buffer transmitted by theSeNB which includes the indicator specifying whether the information isabout available buffer for a UE or about available buffer for anenhanced radio access bearer (E-RAB) on the SeNB.

In accordance with another aspect of the present disclosure, a method ofan MeNB receiving information of an available buffer is provided. Themethod includes receiving, by the MeNB, the information of the availablebuffer via a UE uplink tunnel established on the X2 interface or via auser data bearer corresponding to the E-RAB established on the X2interface.

In accordance with another aspect of the present disclosure, a method ofdeciding the available buffer is available buffer for the UE oravailable buffer for an E-RAB on the SeNB according to a bearer thattransported the information of the available buffer is provided. Themethod includes deciding the available buffer is available buffer for aUE if the information of the available buffer is received from the UEuplink tunnel and deciding the available buffer is available buffer forthe E-RAB if the information of the available buffer is received from auser data bearer corresponding to the E-RAB.

According to an embodiment of the present disclosure, the UE uplinktunnel is established during establishment of the SeNB.

According to an embodiment of the present disclosure, the MeNB informsthe SeNB of a tunnel identifier (ID) of the UE uplink tunnel bytransmitting an add SeNB request including information of the UE uplinktunnel to the SeNB.

According to an embodiment of the present disclosure, the method of theMeNB receiving the information of the available buffer may includereceiving, by the MeNB, the information of the available buffer from auser data bearer on the X2 interface.

In accordance with another aspect of the present disclosure, anindicator in the information of the available buffer is provided. Theindicator includes capabilities information of the SeNB transmitted tothe MeNB in advance by the SeNB or configured in the MeNB in advance forspecifying whether the information of the available buffer transmittedby the SeNB is for the UE or for the E-RAB.

According to an embodiment of the present disclosure, the SeNBtransmitted the capabilities information of the SeNB during the SeNB orthe X2 interface was established.

According to an embodiment of the present disclosure, the information ofthe available buffer is transmitted in a general packet radio servicetunneling protocol user (GTP-U) packet header or in a data packettransmitted in an uplink data tunnel of the user data bearer or in theUE uplink tunnel.

According to an embodiment of the present disclosure, when the SeNBdetermining the information of currently available buffer, the availablebuffer for the UE is determined according to the amount of data packetscurrently in the buffer reserved for the UE and/or the quality of theradio interface between the UE and the SeNB; and/or the available bufferfor the E-RAB is determined according to the amount of data packetscurrently in the buffer reserved for the E-RAB and/or the quality of theradio interface between the UE and the SeNB.

According to an embodiment of the present disclosure, the MeNB mayadjust the amount of data assigned to the SeNB according to the size ofthe available buffer if the information of the available buffer is theavailable buffer for the E-RAB; and/or the MeNB may adjust the amount ofdata assigned to each E-RAB on the SeNB according to quality of service(QoS) and/or priority level of each E-RAB when at least two E-RABs havebeen established on the SeNB if the information of the available bufferis for the UE.

In accordance with another aspect of the present disclosure, anapparatus for assigning data to split bearers in dual connectivity isprovided. The apparatus includes an available buffer deciding module anda data assigning module, the available buffer deciding module isconfigured for receiving information of available buffer decided andtransmitted by an SeNB via an X2 interface to the SeNB, and decidingwhether the information is about available buffer for a UE or about anE-RAB on the SeNB according to an indicator in the information of theavailable buffer or according to a bearer that transported theinformation of the available buffer, and the data assigning module isconfigured for adjusting the amount of data assigned to the SeNBaccording to the received information of the available buffer.

The above technical mechanism provide multiple possible report mannersfor operators, support eNBs provided by different device producers, isadaptable to eNBs implemented in different manners, can effectively usebandwidth of data bearers, and reduce delay in data transmission.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic diagram illustrating a structure of a systemarchitecture evolution (SAE) system according to the related art;

FIG. 2 is a schematic diagram illustrating a cross-evolved node B (eNB)carrier convergence mechanism according to the related art;

FIG. 3 is a flowchart illustrating a method of assigning data accordingto an embodiment of the present disclosure;

FIG. 4 is a flowchart illustrating a method of adjusting assigned dataaccording to an embodiment of the present disclosure;

FIG. 5 is a schematic diagram illustrating a data format according to anembodiment of the present disclosure;

FIG. 6 is a flowchart illustrating a method of adjusting assigned dataaccording to an embodiment of the present disclosure;

FIG. 7 is a flowchart illustrating a method of adjusting assigned dataaccording to an embodiment of the present disclosure;

FIG. 8 is a schematic diagram illustrating modules of an apparatus forassigning data according to an embodiment of the present disclosure;

FIG. 9 is a schematic diagram illustrating a report of data transmissionstatus according to an embodiment of the present disclosure; and

FIG. 10 is a schematic diagram illustrating serial numbers of X2transmissions and packet data convergence protocol (PDCP) packetsaccording to an embodiment of the present disclosure.

The same reference numerals are used to represent the same elementsthroughout the drawings.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

The method of reporting secondary evolved Node B (SeNB) buffer ofvarious examples of the present disclosure provides multiple possiblereport manners for operators, supports eNBs produced by different deviceproducers, is adaptable to different implementations of eNBs, caneffectively use bandwidth of data bearers, and reduce delay in datatransmission. A detailed description of the present disclosure isprovided hereinafter with reference to the some embodiments of thepresent disclosure.

FIG. 3 is a flowchart illustrating a method of assigning data accordingto an embodiment of the present disclosure.

Referring to FIG. 3, the method may include the following operations.

At operation 301, a master eNB (MeNB) of a user equipment (UE) receivesinformation of available buffer decided and transmitted by an SeNB viaan X2 interface between the MeNB and the SeNB.

At operation 302, the MeNB may determine whether the information of theavailable buffer is about available buffer for a UE or about availablebuffer for an evolved radio access bearer (E-RAB) established on theSeNB according to an indicator in the information of the availablebuffer or according to a bearer that transported the information.

As mentioned above, since eNBs may be implemented in different manners,some eNBs allocate buffer for UEs while other eNBs allocate buffer forbearers. Therefore, the MeNB needs to determine whether the informationof the available buffer received is for a UE or for an E-RAB. Variousexamples provide two manners of making the determination. According toone manner, an indicator is used for specifying the type of theavailable buffer. The indicator may be transmitted by the SeNB to theMeNB, or may be configured in the MeNB. According to the other manner,the type of the available buffer is decided based on the position of thebearer that transported the information of the available buffer.

At operation 303, the MeNB adjusts the amount of data assigned to theSeNB according to the received information of the available buffer.

After making a determination as to whether the information of theavailable buffer is about available buffer for a UE or for an E-RAB inoperation 302, the MeNB may decide the amount of data assigned to theSeNB when splitting bearers according to the available buffer.

Then the above process is terminated. According to the mechanism, theMeNB can accommodate SeNBs implemented in different manners, determinewhether the available buffer is for a UE or for an E-RAB, and adjust theamount of data assigned to the SeNB. Therefore, bandwidth of databearers can be used effectively, and delay in data transmission is alsoreduced.

The method is described further in the following with reference to threeexamples. To simplify description, only interactions between an MeNB andan SeNB are described.

Example 1

In this example, an MeNB established a long term evolution (LTE) RAB ofa service on the MeNB and an SeNB, i.e., using the split bearer manner.A user data bearer corresponding to the E-RAB needs to be established onan X2 interface. The user data bearer includes an uplink/downlink datatunnel. The MeNB splits downlink packet data convergence protocol (PDCP)data packets to have some data packets transmitted to the UE by the MeNBand other data packets transmitted via the X2 interface to the SeNBwhich then transmits the data packets to the UE. The user data bearer onthe X2 interface is used for transmitting both user plane PDCP datapackets and information for user traffic flow control which includesinformation of available buffer decided by the SeNB. This exampledescribes a method of the SeNB reporting information of the buffer tothe MeNB via an uplink data tunnel.

FIG. 4 is a flowchart illustrating a method of adjusting assigned dataaccording to an embodiment of the present disclosure.

Referring to FIG. 4, the process may include the following operations.

At operation 401, an SeNB transmits information of decided availablebuffer to an MeNB.

The information of the available buffer is transmitted in an uplink datatunnel in a user data bearer corresponding to an E-RAB. The informationmay be transmitted alone or together with a data packet. The uplink datatunnel is established during a process of adding or modifying the SeNB.The process may include the MeNB transmitting an add/modify SeNB requestwhich includes information of the quality of a radio data bearer, anInternet protocol (IP) address and a tunnel identifier (ID) for uplinkdata reception, information of capabilities of a UE, configurationinformation of resources on the MeNB, and the like. The SeNB maytransmit to the MeNB a response which includes configuration informationof the radio data bearer, an IP address and a tunnel ID for downlinkdata reception, and the like. The information of the available buffer ofthe SeNB is transmitted to the MeNB via the established uplink datatunnel.

The information of the available buffer may be transmitted in the headeror the data packet field of a general packet radio service tunnelingprotocol user (GTP-U) packet through the uplink data tunnel. Theinformation of the available buffer specifies buffer available in theSeNB in units of bit or Byte. The bigger the available buffer, the moredata the SeNB can receive, i.e., the MeNB can assign more data to theSeNB. The available buffer may refer to available buffer for an E-RAB,i.e., available buffer allocated to the E-RAB, and information of theavailable buffer is transmitted to the MeNB via an uplink data tunnel ofthe E-RAB. Alternatively, the available buffer may refer to availablebuffer for a UE, i.e., available buffer allocated to all of bearersestablished on the SeNB for a UE, and information of the availablebuffer is transmitted to the MeNB via an uplink data tunnel of one ofthe bearers, or the same information may be transmitted in uplink datatunnels of all the bearers to the MeNB. The information may be as shownin FIG. 5.

FIG. 5 is a schematic diagram illustrating a data format according to anembodiment of the present disclosure.

Referring to FIG. 5, information of available buffer of an SeNB may bespecified using 8 bits or data of another length. The most significantbit specifies whether the buffer is for a UE or for an E-RAB. Forexample, a value of “1” indicates the information is about availablebuffer for a UE, and a value of “0” indicates the information is aboutavailable buffer for an E-RAB. Subsequent 7 bits shown in FIG. 5indicate the number of bits of the available buffer. Alternatively, theindicator may be placed in the reserved bit next to the packet data unit(PDU) type. The one bit indicates whether the available buffer is for anE-RAB or for all of E-RABs, i.e., for the UE. For example, a reservedbit is used for indicating whether there is the buffer for the UE. Thebit set to 1 indicates the format as shown in FIG. 5 includesinformation of buffer for the UE, and the bit set to 0 indicates theformat as shown in FIG. 5 does not include information of the buffer forthe UE. Another reserved bit is used for indicating whether there is thebuffer for the E-RAB. The bit set to 1 indicates the format as shown inFIG. 5 includes information of buffer for the E-RAB, and the bit set to0 indicates the format as shown in FIG. 5 does not include informationof the buffer for the E-RAB. If both types of buffers are configured inthe format, the order of the indicators and the order of the two bufferformats needs to be specified. For example, buffer information of theE-RAB may precede buffer information of the UE, and the indicatorsarranged in the same order.

The size of the available buffer for a UE may be determined based on thenumber of packets buffered in the buffer reserved for the UE (i.e., thenumber of packets currently in the buffer reserved for the UE). The morethe data packets are, the less the available buffer is. This is becausethe SeNB needs to first transmit out the already buffered data packets.The more data packets buffered, the less data packets the SeNB expect toreceive.

The SeNB may also decide the size of the available buffer for a UE basedon the quality of a radio interface between the UE and the SeNB. In anexample, the SeNB may receive a quality report of the radio interfacefrom the UE. If the radio interface is of poor quality, the SeNB mayexpect to receive not many data packets even if the available buffer islarge. Due to reasons of quality control, the data packets cannot reachthe UE within a short time.

The SeNB may decide the size of available buffer for an E-RAB accordingto the number of packets buffered in the reserved buffer (i.e., thenumber of data packets currently in the buffer reserved for the E-RAB),or according to the quality of a radio interface between the UE and theSeNB.

At operation 402, the MeNB adjusts the amount of data assigned to theSeNB.

The MeNB may use the information of the available buffer transmitted bythe SeNB together with other information. For example, the SeNB may alsoreport information of PDCP data packets that have been transmitted tothe UE successfully, and the MeNB may delete the data packets from thebuffer in the MeNB. The MeNB may decide the amount of data assigned tothe SeNB according to the size of the buffer for the user in the SeNBand the amount of data stored in the MeNB. In an example, if theavailable buffer is relatively small, the MeNB may reduce the amount ofdata assigned to the SeNB; and if the available buffer is relativelylarge, the MeNB may increase the amount of data assigned to the SeNB.

If the available buffer is for a UE and plural bearers have beenestablished on the SeNB, the MeNB may decide the bearer on which theamount of data is to be adjusted, i.e., the bearer whose split ratio isto be adjusted, according to the quality of service (QoS) and thepriority level of the E-RAB.

Example 2

Example 1 describes transmitting buffer information to an MeNB via auser data bearer on an X2 interface. Example 2 describes a mechanism inwhich an MeNB does not know the implementation method of an SeNB, and auser plane is established for an X2 interface when a split bearer isestablished. The user plane is for transmitting buffer information for aUE, and is not associated with any E-RAB. If the SeNB allocates bufferaccording to UEs, information of the size of available buffer istransmitted via the user plane. If the SeNB allocates buffer accordingto bearers, the information of the size of available buffer istransmitted via a user data plane corresponding to an E-RAB on the X2interface.

FIG. 6 is a flowchart illustrating a method of adjusting assigned dataaccording to an embodiment of the present disclosure.

Referring to FIG. 6, the process may include the following operations.

At operation 601, an MeNB transmits an add SeNB request to an SeNB.

The MeNB decides to request the SeNB to establish radio resources for anE-RAB of a UE. The message also results in generation of UE context inthe SeNB. The message may include information, such as information ofthe E-RAB, e.g., an identifier of the E-RAB, an identifier of the radioresources, quality information, information of an uplink data tunnelincluding an IP address and a tunnel ID on the user plane, informationof capabilities of the UE, resource configuration information in theMeNB, and the like. The message may also include information of a UEuplink tunnel. The UE uplink tunnel is not associated with the E-RAB,may include an IP address and a tunnel ID, or only include the tunnelID. The UE uplink tunnel is used for receiving the information of thesize of available buffer allocated by the SeNB for the UE.

At operation 602, the SeNB transmits an add SeNB response to the MeNB.

The response transmitted by the SeNB to the MeNB may includeconfiguration information and a radio resource control (RRC) containerof a radio bearer that has been successfully established, and an IPaddress and a tunnel ID for downlink data reception of the bearer.

At operation 603, the MeNB transmits a modify SeNB request to the SeNB.

The MeNB decides to request the SeNB to establish radio resources for asecond E-RAB of the UE. The request may include information of thesecond E-RAB, e.g., an identifier of the E-RAB, an identity of the radioresources, quality information. The request may also include an IPaddress and a tunnel ID for uplink data reception, information ofcapabilities of the UE, resource configuration information in the MeNB,and the like.

At operation 604, the SeNB transmits a modified SeNB response to theMeNB.

The response transmitted by the SeNB to the MeNB may includeconfiguration information and an RRC container of a radio bearer thathas been successfully established, and an IP address and a tunnel ID fordownlink data reception of the bearer.

At operation 605, the SeNB transmits buffer information to the MeNB.

If the buffer of the SeNB is allocated for an E-RAB, the information ofthe available buffer is transmitted through an uplink data tunnel in auser data bearer corresponding to the E-RAB. The information may betransmitted alone or together with a data packet. The uplink data tunnelis established during an add/modify SeNB process. The information of theavailable buffer of the SeNB is transmitted to the MeNB via theestablished uplink data tunnel.

If the buffer is allocated by the SeNB for the UE, the information ofthe available buffer is transmitted through a UE uplink tunnel. The UEuplink tunnel is established during the process of establishing theSeNB.

The information of the available buffer may be transmitted in the headeror the data packet field of a GTP-U packet through the uplink tunnel.The uplink tunnel may be the UE uplink tunnel or the uplink data tunnelin the user data bearer.

The SeNB may adopt the same manner as in Example 1 for deciding the sizeof the available buffer.

In an example, the size of the available buffer for a UE may bedetermined based on the number of packets buffered in the bufferreserved for the UE (i.e., the number of packets currently in the bufferreserved for the UE). The more the data packets are, the less theavailable buffer is. This is because the SeNB needs to first transmitout the already buffered data packets. The more data packets buffered,the less data packets the SeNB expect to receive.

The SeNB may also decide the size of the available buffer for a UE basedon the quality of a radio interface between the UE and the SeNB. In anexample, the SeNB may receive a quality report of the radio interfacefrom the UE. If the radio interface is of poor quality, the SeNB mayexpect to receive not many data packets even if the available buffer islarge. Due to reasons of quality control, the data packets cannot reachthe UE in a short time.

The SeNB may decide the size of available buffer for an E-RAB accordingto the number of packets buffered in the reserved buffer (i.e., thenumber of data packets currently in the buffer reserved for the E-RAB),or according to the quality of a radio interface between the UE and theSeNB.

At operation 606, the MeNB adjusts the amount of data assigned to theSeNB.

The MeNB may use the information of the available buffer transmitted bythe SeNB together with other information. For example, the SeNB may alsoreport information of PDCP data packets that have been transmitted tothe UE successfully, and the MeNB may delete the data packets from thebuffer in the MeNB. The MeNB may decide the amount of data assigned tothe SeNB according to the size of the buffer for the user in the SeNBand the amount of data stored in the MeNB. In an example, if theavailable buffer is relatively small, the MeNB may reduce the amount ofdata assigned to the SeNB; and if the available buffer is relativelylarge, the MeNB may increase the amount of data assigned to the SeNB.

If the available buffer is for a UE and plural bearers have beenestablished on the SeNB, the MeNB decides a bearer for which the amountof data is to be adjusted, i.e., the bearer whose split ratio is to beadjusted, according to the QoS and the priority level of the E-RAB.

Hence, the process of the example is completed. In this example, a UEuplink tunnel is established on the X2 interface for transmittinginformation of available buffer for the UE. The UE uplink tunnel isestablished during the process of establishing the SeNB. In otherexamples, the UE uplink tunnel may be established in other processes, orestablished in an individual process.

Example 3

According to Example 3, an SeNB informs an MeNB of whether the availablebuffer in the SeNB is for an UE or for an E-RAB. Thus, the MeNB knowsthe implementation method of the SeNB before receiving the informationof available buffer. Information of the size of available buffer in theSeNB is transmitted through a data plane corresponding to the E-RAB onan X2 interface. Since the MeNB knows the method adopted by the SeNB,the MeNB knows the buffer information is for the UE or for the bearer.

FIG. 7 is a flowchart illustrating a method of adjusting assigned dataaccording to an embodiment of the present disclosure.

Referring to FIG. 7, the process may include the following operations.

At operation 701, an MeNB transmits an add SeNB request to an SeNB.

The MeNB decides to request the SeNB to establish radio resources for anE-RAB of a UE. The message also results in generation of UE context inthe SeNB. The message may include information, such as information ofthe E-RAB, e.g., an identifier of the E-RAB, an identifier of the radioresources, quality information, information of an uplink data tunnel, anIP address and a tunnel ID on the user plane, information ofcapabilities of the UE, resource configuration information in the MeNB,and the like.

At operation 702, the SeNB transmits an add SeNB response to the MeNB.

The response transmitted by the SeNB to the MeNB may includeconfiguration information and an RRC container of a radio bearer thathas been successfully established, and an IP address and a tunnel ID fordownlink data reception of the bearer. The response may also includeinformation of capabilities of the SeNB which specifies whether theinformation of available buffer is for the UE or for an E-RAB.

The information may also be transmitted during the establishment of theX2 interface between the MeNB and the SeNB. The MeNB transmits an X2setup request, and the SeNB transmits an X2 setup response to the MeNB.The X2 setup response may include the information of capabilities of theSeNB which indicates whether reports of buffer information are for theUE or for an E-RAB. Alternatively, the SeNB may transmit an X2 setuprequest to the MeNB, and the X2 setup response may include theinformation of capabilities of the SeNB which indicates whether reportsof buffer information are for the UE or for an E-RAB.

In another example, the capability information may be configured in theMeNB in advance. The MeNB may get information on whether reports fromthe SeNB regarding available buffer are for the UE or for an E-RAB fromOAM configuration information received in advance.

At operation 703, the SeNB transmits buffer information to the MeNB.

The buffer information is transmitted via an uplink data tunnel. Thebuffer information may be transmitted together with a data packet ortransmitted individually. The uplink data tunnel is established duringan add/modify SeNB process. The buffer information of the SeNB istransmitted to the MeNB via the established uplink data tunnel.

The information of available buffer may be transmitted in the header orthe data packet field of a GTP-U packet through the uplink data tunnel.

The SeNB may adopt the same manner as in Example 1 for deciding the sizeof the available buffer.

The size of the available buffer for a UE may be determined based on thenumber of packets buffered in the buffer reserved for the UE (i.e., thenumber of packets currently in the buffer reserved for the UE). The morethe data packets are, the less the available buffer is. This is becausethe SeNB needs to first transmit out the already buffered data packets.The more data packets already buffered, the less data packets the SeNBexpects to receive.

The SeNB may also decide the size of the available buffer for a UE basedon the quality of a radio interface between the UE and the SeNB. In anexample, the SeNB may receive a quality report of the radio interfacefrom the UE. If the radio interface is of poor quality, the SeNB mayexpect to receive not many data packets even if the available buffer islarge. Due to reasons of quality control, the data packets cannot reachthe UE in a short time.

The SeNB may decide the size of available buffer for an E-RAB accordingto the number of packets buffered in the reserved buffer (i.e., thenumber of data packets currently in the buffer reserved for the E-RAB),or according to the quality of a radio interface between the UE and theSeNB.

At operation 704, the MeNB adjusts the amount of data assigned to theSeNB.

The MeNB may use the information of the available buffer transmitted bythe SeNB together with other information. For example, the SeNB may alsoreport information of PDCP data packets that have been transmitted tothe UE successfully, and the MeNB may delete the data packets from thebuffer in the MeNB. The MeNB may decide the amount of data assigned tothe SeNB according to the size of the buffer for the user in the SeNBand the amount of data stored in the MeNB. In an example, if theavailable buffer is relatively small, the MeNB may reduce the amount ofdata assigned to the SeNB; and if the available buffer is relativelylarge, the MeNB may increase the amount of data assigned to the SeNB.

If the available buffer is for a UE and plural bearers have beenestablished on the SeNB, the MeNB decides the bearer on which the amountof data is to be adjusted, i.e., the bearer whose split ratio is to beadjusted, according to the QoS and the priority level of the E-RAB.

Hence, the process of the example is completed.

Example 4

In Example 4, an SeNB may also report information of lost packetstransmitted via the X2 interface and the largest PDCP serial number ofsequentially transmitted PDCP packets when reporting the bufferinformation. The report is referred to as downlink data transmissionstate report.

FIG. 9 is a schematic diagram illustrating a report of data transmissionstatus according to an embodiment of the present disclosure.

Referring to FIG. 9, the downlink data transmission state reported bythe SeNB may include the information of lost packets transmitted via theX2 interface and the largest PDCP serial number of sequentiallytransmitted PDCP packets. The MeNB transmits PDCP packets to the SeNBvia the X2 interface. A serial number of the X2 interface, referred toas X2 SN, is added to each of the PDCP packets by the MeNB. The X2 SN issequentially numbered. Each PDCP packet has a PDCP serial number (PDCPSN). PDCP packets transmitted by the MeNB to the SeNB may havesequential or non-sequential serial numbers.

FIG. 10 is a schematic diagram illustrating serial numbers of X2transmissions and PDCP packets according to an embodiment of the presentdisclosure.

Referring to FIG. 10, PDCP SN corresponding to X2 SN={7, 8, 9, 10, 11,12} is {1007, 1008, 1009, 1010, 1011, 1012}. According to mechanisms ofthe related art, supposing an SeNB received packets whose X2 SN=7, 11,12, the SeNB may determine that packets whose X2 SN={8, 9, 10} are lostin X2 transmission. The SeNB may report the packet loss to the MeNB. TheMeNB may adopt corresponding measures, e.g., the MeNB may transmit thePDCP packets whose X2 SN={8, 9, 10} to the UE.

According to the mechanisms of the related art, suppose packets whose X2SN={7, 8, 9, 10, 11, 12} were received by the SeNB, and the SeNB hadstarted to transmit the packets to the UE. PDCP packets whose X2 SN={7,8, 12} had been transmitted successfully to the UE, and PDCP packetswhose X2 SN={9, 10, 11} had been transmitted to the UE but were notsuccessfully received by the UE thus the SeNB was re-transmitting thePDCP packets. At that moment, the MeNB initiated a bearer releaseprocess to delete the bearer from the SeNB. The SeNB needed to reportthe last data transmission state to the MeNB. Since no packet was loston the X2 interface, in the report transmitted by the SeNB for theexample as shown in FIG. 10 according to mechanisms of the related art,the largest PDCP serial number of sequentially transmitted PDCP packetsis 1008, and the report does not include information of lost packetstransmitted via the X2 interface. The MeNB received the report,determined that transmission of PDCP packets whose PDCP SN={9, 10, 11,12} has failed, and would re-transmit PDCP packets whose PDCP SN={9, 10,11, 12} to the UE. But in fact, the PDCP packet whose PDCP SN={12} hadbeen transmitted successfully. The re-transmission is unnecessary.

In order to address the issue, when the SeNB reports the last datatransmission state to the MeNB, the largest PDCP serial number of PDCPpackets sequentially transmitted is set to be the PDCP serial number ofthe last PDCP packet successfully transmitted to the UE instead of thePDCP serial number of sequentially transmitted PDCP packets, theinformation of lost packets transmitted over the X2 interface is set toinclude information of lost packets on the X2 interface and informationof packets being re-transmitted by the SeNB. According to the example asshown in FIG. 10, the largest PDCP serial number of packets successfullytransmitted to the UE by the SeNB is 1012. The SeNB reports informationof PDCP packets that have not been successfully transmitted to the UE atthat moment, including X2 SN of packets lost on the X2 interface and X2SN of packets being re-transmitted (i.e., packets that have beensuccessfully received by the SeNB via X2 and have been transmitted tothe UE but the UE has not received thus are being re-transmitted), tothe MeNB as information of lost packets in the X2 interface.

For example, information of lost packet on the X2 interface in the lastdata transmission state report includes information of packets that arebeing re-transmitted.

If the SeNB has both to-be-retransmitted packets and packets lost overthe X2 interface when the bearer is to be released, information of thepackets is reported to the MeNB via information of lost packetstransmitted over the X2 interface in the data transmission state report.

The information of packets lost on the X2 interface are reported using arange between serial numbers, i.e., using the serial number of the firstlost packet and the serial number of the last lost packet. In theexample as shown in FIG. 10, if the serial numbers of packets lost overthe X2 interface are X2 SN={9, 10, 11}, the information of lost packetson the X2 interface is {8, 12}. The last data transmission state isreported using the same manner. In the example as shown in FIG. 10, ifserial numbers of packets that are being re-transmitted are X2 SN={9,10, 11}, the information of packets lost on the X2 interface in the lastdata transmission state is {8, 12}.

The above are several examples of the data assigning method of thepresent disclosure. Various examples also provide an apparatus forassigning data to split bearers in dual connectivity which can implementthe method of various example.

FIG. 8 is a schematic diagram illustrating modules of an apparatus forassigning data according to an embodiment of the present disclosure.

Referring to FIG. 8, the apparatus may include an available bufferdeciding module and a data amount assigning module.

The available buffer deciding module is configured for receivinginformation of available buffer decided and transmitted by an SeNB viaan X2 interface, and deciding whether the information is about availablebuffer for a UE or for an E-RAB established on the SeNB according to anindicator in the information of the available buffer or according to abearer that transported the information of the available buffer. Thedata assigning module is configured for adjusting the amount of dataassigned to the SeNB according to the received information of theavailable buffer.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method of a first base station, the methodcomprising: receiving, via an X2 interface between the first basestation and a second base station from the second based station, firstinformation on a buffer for an evolved universal terrestrial radioaccess network (E-UTRAN) radio access bearer (E-RAB), second informationon a buffer for a terminal which is associated with the first basestation and the second base station, and third information on packetslost in X2 transmission between the first base station and the secondbase station; and adjusting an amount of data to be assigned to thesecond base station based on the first information, the secondinformation and the third information.
 2. The method of claim 1, themethod comprising: retransmitting packets corresponding to the lostpackets based on the third information.
 3. The method of claim 1,wherein the third information includes information on a sequence numberassociated with the lost packets.
 4. The method of claim 1, wherein thethird information is received in a downlink data transmission statereport.
 5. The method of claim 1, wherein fourth information on packetdata convergence protocol (PDCP) data packets successfully received bythe second base station is received from the second base station withthe first information, the second information and the third information.6. The method of claim 5, further comprising: deleting the PDCP datapackets successfully received by the second base station from a bufferof the first base station.
 7. A method of a second base station, themethod comprising: generating first information on a buffer for anevolved universal terrestrial radio access network (E-UTRAN) radioaccess bearer (E-RAB), second information on a buffer for a terminalwhich is associated with a first base station and the second basestation, and third information on packets lost in X2 transmissionbetween the first base station and the second base station; andtransmitting, via an X2 interface between the first base station and thesecond base station to the first base station, the first information,the second information and the third information.
 8. The method of claim7, wherein the third information includes information on a sequencenumber associated with the lost packets.
 9. The method of claim 7,wherein the third information is transmitted in a downlink datatransmission state report.
 10. The method of claim 7, wherein fourthinformation on packet data convergence protocol (PDCP) data packetssuccessfully received by the second base station is transmitted to thefirst base station with the first information, the second informationand the third information.
 11. A first base station in a wirelesscommunication system, the first base station comprising: a transceiverconfigured to transmit and receive signals to and from a second basestation and a terminal which is associated with the first base stationand the second base station; and a processor configured to: control thetransceiver to receive, via an X2 interface between the first basestation and the second base station from the second based station, firstinformation on a buffer for an evolved universal terrestrial radioaccess network (E-UTRAN) radio access bearer (E-RAB), second informationon a buffer for a terminal which is associated with the first basestation and the second base station, and third information on packetslost in X2 transmission between the first base station and the secondbase station, and adjust an amount of data to be assigned to the secondbase station based on the first information, the second information andthe third information.
 12. The first base station of claim 11, whereinthe processor is further configured to control the transceiver toretransmit packets corresponding to the lost packets based on the thirdinformation.
 13. The first base station of claim 11, wherein the thirdinformation includes information on a sequence number associated withthe lost packets.
 14. The first base station of claim 11, wherein theprocessor is further configured to control the transceiver to receivethe third information in a downlink data transmission state report. 15.The first base station of claim 11, wherein the processor is furtherconfigured to control the transceiver to receive fourth information onpacket data convergence protocol (PDCP) data packets successfullyreceived by the second base station from the second base station withthe first information, the second information and the third information.16. The first base station of claim 11, wherein the processor is furtherconfigured to delete the PDCP data packets successfully received by thesecond base station from a buffer of the first base station.
 17. Asecond base station in a wireless communication system, the second basestation comprising: a transceiver configured to transmit and receivesignals to and from a first base station and a terminal which isassociated with the first base station and the second base station; anda processor configured to: generate first information on a buffer for anevolved universal terrestrial radio access network (E-UTRAN) radioaccess bearer (E-RAB), second information on a buffer for a terminalwhich is associated with a first base station and the second basestation, and third information on packets lost in X2 transmissionbetween the first base station and the second base station, and controlto the transceiver to transmit, via an X2 interface between the firstbase station and the second base station to the first base station, thefirst information, the second information and the third information. 18.The second base station of claim 17, wherein the third informationincludes information on a sequence number associated with the lostpackets.
 19. The second base station of claim 17, wherein the processoris further configured to control the transceiver to transmit the thirdinformation in a downlink data transmission state report.
 20. The secondbase station of claim 17, wherein the processor is further configured tocontrol the transceiver to transmit fourth information on packet dataconvergence protocol (PDCP) data packets successfully received by thesecond base station to the first base station with the firstinformation, the second information and the third information.